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Commit ba7443bc authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
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sysfs, kernfs: implement kernfs_create/destroy_root() 



There currently is single kernfs hierarchy in the whole system which
is used for sysfs.  kernfs needs to support multiple hierarchies to
allow other users.  This patch introduces struct kernfs_root which
serves as the root of each kernfs hierarchy and implements
kernfs_create/destroy_root().

* Each kernfs_root is associated with a root sd (sysfs_dentry).  The
  root is freed when the root sd is released and kernfs_destory_root()
  simply invokes kernfs_remove() on the root sd.  sysfs_remove_one()
  is updated to handle release of the root sd.  Note that ps_iattr
  update in sysfs_remove_one() is trivially updated for readability.

* Root sd's are now dynamically allocated using sysfs_new_dirent().
  Update sysfs_alloc_ino() so that it gives out ino from 1 so that the
  root sd still gets ino 1.

* While kernfs currently only points to the root sd, it'll soon grow
  fields which are specific to each hierarchy.  As determining a given
  sd's root will be necessary, sd->s_dir.root is added.  This backlink
  fits better as a separate field in sd; however, sd->s_dir is inside
  union with space to spare, so use it to save space and provide
  kernfs_root() accessor to determine the root sd.

* As hierarchies may be destroyed now, each mount needs to hold onto
  the hierarchy it's attached to.  Update sysfs_fill_super() and
  sysfs_kill_sb() so that they get and put the kernfs_root
  respectively.

* sysfs_root is replaced with kernfs_root which is dynamically created
  by invoking kernfs_create_root() from sysfs_init().

This patch doesn't introduce any visible behavior changes.

v2: kernfs_create_root() forgot to set @sd->priv.  Fixed.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 061447a4

fs/kernfs/dir.c

+62 −9
Original line number Diff line number Diff line
@@ -211,7 +211,7 @@ static int sysfs_alloc_ino(unsigned int *pino) 


 retry:

	spin_lock(&sysfs_ino_lock);

	rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino);

	rc = ida_get_new_above(&sysfs_ino_ida, 1, &ino);

	spin_unlock(&sysfs_ino_lock);



	if (rc == -EAGAIN) {
@@ -253,9 +253,11 @@ EXPORT_SYMBOL_GPL(kernfs_get); 
void kernfs_put(struct sysfs_dirent *sd)

{

	struct sysfs_dirent *parent_sd;

	struct kernfs_root *root;



	if (!sd || !atomic_dec_and_test(&sd->s_count))

		return;

	root = kernfs_root(sd);

 repeat:

	/* Moving/renaming is always done while holding reference.

	 * sd->s_parent won't change beneath us.
@@ -278,8 +280,13 @@ void kernfs_put(struct sysfs_dirent *sd) 
	kmem_cache_free(sysfs_dir_cachep, sd);



	sd = parent_sd;

	if (sd && atomic_dec_and_test(&sd->s_count))

	if (sd) {

		if (atomic_dec_and_test(&sd->s_count))

			goto repeat;

	} else {

		/* just released the root sd, free @root too */

		kfree(root);

	}

}

EXPORT_SYMBOL_GPL(kernfs_put);
@@ -493,13 +500,15 @@ static void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, 
	if (sd->s_flags & SYSFS_FLAG_REMOVED)

		return;



	if (sd->s_parent) {

		sysfs_unlink_sibling(sd);



		/* Update timestamps on the parent */

		ps_iattr = sd->s_parent->s_iattr;

		if (ps_iattr) {

		struct iattr *ps_iattrs = &ps_iattr->ia_iattr;

		ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;

			ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;

			ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;

		}

	}



	sd->s_flags |= SYSFS_FLAG_REMOVED;
@@ -603,6 +612,49 @@ struct sysfs_dirent *kernfs_find_and_get_ns(struct sysfs_dirent *parent, 
}

EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);



/**

 * kernfs_create_root - create a new kernfs hierarchy

 * @priv: opaque data associated with the new directory

 *

 * Returns the root of the new hierarchy on success, ERR_PTR() value on

 * failure.

 */

struct kernfs_root *kernfs_create_root(void *priv)

{

	struct kernfs_root *root;

	struct sysfs_dirent *sd;



	root = kzalloc(sizeof(*root), GFP_KERNEL);

	if (!root)

		return ERR_PTR(-ENOMEM);



	sd = sysfs_new_dirent("", S_IFDIR | S_IRUGO | S_IXUGO, SYSFS_DIR);

	if (!sd) {

		kfree(root);

		return ERR_PTR(-ENOMEM);

	}



	sd->s_flags &= ~SYSFS_FLAG_REMOVED;

	sd->priv = priv;

	sd->s_dir.root = root;



	root->sd = sd;



	return root;

}



/**

 * kernfs_destroy_root - destroy a kernfs hierarchy

 * @root: root of the hierarchy to destroy

 *

 * Destroy the hierarchy anchored at @root by removing all existing

 * directories and destroying @root.

 */

void kernfs_destroy_root(struct kernfs_root *root)

{

	kernfs_remove(root->sd);	/* will also free @root */

}



/**

 * kernfs_create_dir_ns - create a directory

 * @parent: parent in which to create a new directory
@@ -626,6 +678,7 @@ struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent, 
	if (!sd)

		return ERR_PTR(-ENOMEM);



	sd->s_dir.root = parent->s_dir.root;

	sd->s_ns = ns;

	sd->priv = priv;

fs/kernfs/kernfs-internal.h

+20 −0
Original line number Diff line number Diff line
@@ -25,6 +25,12 @@ struct sysfs_elem_dir { 
	unsigned long		subdirs;

	/* children rbtree starts here and goes through sd->s_rb */

	struct rb_root		children;



	/*

	 * The kernfs hierarchy this directory belongs to.  This fits

	 * better directly in sysfs_dirent but is here to save space.

	 */

	struct kernfs_root	*root;

};



struct sysfs_elem_symlink {
@@ -104,6 +110,20 @@ static inline unsigned int sysfs_type(struct sysfs_dirent *sd) 
	return sd->s_flags & SYSFS_TYPE_MASK;

}



/**

 * kernfs_root - find out the kernfs_root a sysfs_dirent belongs to

 * @sd: sysfs_dirent of interest

 *

 * Return the kernfs_root @sd belongs to.

 */

static inline struct kernfs_root *kernfs_root(struct sysfs_dirent *sd)

{

	/* if parent exists, it's always a dir; otherwise, @sd is a dir */

	if (sd->s_parent)

		sd = sd->s_parent;

	return sd->s_dir.root;

}



/*

 * Context structure to be used while adding/removing nodes.

 */

fs/sysfs/mount.c

+18 −11
Original line number Diff line number Diff line
@@ -32,15 +32,8 @@ static const struct super_operations sysfs_ops = { 
	.evict_inode	= sysfs_evict_inode,

};



static struct sysfs_dirent sysfs_root = {

	.s_name		= "",

	.s_count	= ATOMIC_INIT(1),

	.s_flags	= SYSFS_DIR,

	.s_mode		= S_IFDIR | S_IRUGO | S_IXUGO,

	.s_ino		= 1,

};



struct sysfs_dirent *sysfs_root_sd = &sysfs_root;

static struct kernfs_root *sysfs_root;

struct sysfs_dirent *sysfs_root_sd;



static int sysfs_fill_super(struct super_block *sb)

{
@@ -68,6 +61,7 @@ static int sysfs_fill_super(struct super_block *sb) 
		pr_debug("%s: could not get root dentry!\n", __func__);

		return -ENOMEM;

	}

	kernfs_get(sysfs_root_sd);

	root->d_fsdata = sysfs_root_sd;

	sb->s_root = root;

	sb->s_d_op = &sysfs_dentry_ops;
@@ -138,11 +132,15 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type, 
static void sysfs_kill_sb(struct super_block *sb)

{

	struct sysfs_super_info *info = sysfs_info(sb);

	/* Remove the superblock from fs_supers/s_instances

	struct sysfs_dirent *root_sd = sb->s_root->d_fsdata;



	/*

	 * Remove the superblock from fs_supers/s_instances

	 * so we can't find it, before freeing sysfs_super_info.

	 */

	kill_anon_super(sb);

	free_sysfs_super_info(info);

	kernfs_put(root_sd);

}



static struct file_system_type sysfs_fs_type = {
@@ -166,12 +164,21 @@ int __init sysfs_init(void) 
	if (err)

		goto out_err;



	sysfs_root = kernfs_create_root(NULL);

	if (IS_ERR(sysfs_root)) {

		err = PTR_ERR(sysfs_root);

		goto out_err;

	}

	sysfs_root_sd = sysfs_root->sd;



	err = register_filesystem(&sysfs_fs_type);

	if (err)

		goto out_err;

		goto out_destroy_root;



	return 0;



out_destroy_root:

	kernfs_destroy_root(sysfs_root);

out_err:

	kmem_cache_destroy(sysfs_dir_cachep);

	sysfs_dir_cachep = NULL;

include/linux/kernfs.h

+13 −0
Original line number Diff line number Diff line
@@ -20,6 +20,11 @@ struct vm_area_struct; 


struct sysfs_dirent;



struct kernfs_root {

	/* published fields */

	struct sysfs_dirent	*sd;

};



struct sysfs_open_file {

	/* published fields */

	struct sysfs_dirent	*sd;
@@ -76,6 +81,9 @@ struct sysfs_dirent *kernfs_find_and_get_ns(struct sysfs_dirent *parent, 
void kernfs_get(struct sysfs_dirent *sd);

void kernfs_put(struct sysfs_dirent *sd);



struct kernfs_root *kernfs_create_root(void *priv);

void kernfs_destroy_root(struct kernfs_root *root);



struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent,

					  const char *name, void *priv,

					  const void *ns);
@@ -107,6 +115,11 @@ kernfs_find_and_get_ns(struct sysfs_dirent *parent, const char *name, 
static inline void kernfs_get(struct sysfs_dirent *sd) { }

static inline void kernfs_put(struct sysfs_dirent *sd) { }



static inline struct kernfs_root *kernfs_create_root(void *priv)

{ return ERR_PTR(-ENOSYS); }



static inline void kernfs_destroy_root(struct kernfs_root *root) { }



static inline struct sysfs_dirent *

kernfs_create_dir_ns(struct sysfs_dirent *parent, const char *name, void *priv,

		     const void *ns)